This invention is concerned with the design of binary optical lenses.
The modulation of an optical wavefront by a surface relief pattern has the remarkable capability of generating an arbitrary image from a single incident plane wave. One example of such modulation in the prior art is a binary phase-only filter for optical correlation, where the phase relief pattern was generated by taking the Fourier transform of a given image (Flavin, et al., Correlation Experiments with a Binary Phase-Only Filter Implemented on a Quartz Substrate, Optical Engineering, Volume 28, Pages 470-473 (1989). Another example involved the generation of an array of equal spots for optical computing devices, with the relief pattern generated using a Monte Carlo type iterative method, known as simulated annealing, to arrive at a pattern which would generate an array of spots (Feldman, et al., Iterative Encoding of High-Efficiency Holograms for Generation of Spot Arrays, Optics Letters, Volume 14, Pages 479-481 (1989). Unlike a conventional optical surface, whose profile is characterized by only a few variables, a binary optical surface consists of a large number of discontinuous subaperture regions. The desired optical effect of a lens is achieved by virtue of imposing a difference in phase of .pi. radians between adjacent regions of the binary lens. The resulting interference effects between light passing through the various regions provides the means to produce a lens.
Because of the large number of subaperture regions which must be analyzed in designing a binary optical lens, conventional ray tracing design techniques are cumbersome for binary optical design and may not achieve an optimal solution in any event. Thus it would be desirable to provide an alternative technique for generating an arbitrary intensity pattern resulting from down-field propagation of a plane wave incident on a binary phase relief pattern.